This invention relates to an apparatus and method for stimulating producing zones of an openhole wellbore in oil and gas wells. More particularly, the invention relates to an assembly for selectively stimulating a wellbore without the use of openhole inflatable packers. The assembly is especially suited to perform a combination of matrix acidizing jobs and near wellbore erosion jobs at a number of producing zones in the wellbore in a single trip.
Previously, operators who were interested in stimulating multiple producing zones in an openhole wellbore could stimulate the zones one zone at a time by using a workstring and an openhole inflatable packer. Such a method and assembly required the operator to set an inflatable packer (or other similar apparatus) above each zone of interest to be stimulated and then, following the stimulation job, to release the packer (or packers) and trip the packer assembly to a new location where it would be reset for the next stimulation job. This procedure would be repeated for each desired zone of interest. However, because of the tripping time and the difficulty in setting and maintaining the seal in inflatable packers in openhole wellbores, such a method was both time consuming and relatively unreliable. Furthermore, openhole inflatable packers (or other similar devices) are expensive to rent or to purchase. As a result of the relative unreliability and cost of using openhole inflatable packers, such assemblies prove to be uneconomical in marginal fields such as fields in the Permian Basin region of West Texas and Eastern New Mexico.
The assembly of the present invention does not require an inflatable packer and is very economical to build and maintain. Thus, an operator can use the present invention for a small incremental cost over what it costs to perform an acid job and receives the benefits of not only a matrix acidizing treatment, but can also enhance the flow in the near wellbore region by eroding away near wellbore skin damage. In addition, the present invention allows an operator to accurately position an assembly in a wellbore to ensure that the producing zones of interest are stimulated.